International System of Units

Historical eventMay 202019

International System of Units

The International System of Units (SI): The base units are redefined, making the international prototype of the kilogram obsolete.

Everything on May 20Original source
Photo: Martinvl · CC BY-SA 3.0

In context

When
Monday, May 20 20197 years ago
Category
Historical eventA dated happening — a battle, treaty, launch, discovery, disaster or decision — recorded on this calendar day.
Era
21st century · 2010s
Recorded from
Wikipedia “On this day” feed

At a glance

Dates: From 2019.

Type: international standard, technical standard, coherent system of units, and metric system.

What happened

The International System of Units, internationally known by the abbreviation SI, is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce. The International Bureau of Weights and Measures coordinates the SI.

May 20 through the years

Other entries on the same calendar day, in order.

  1. 1996Romer v. Evans
  2. 1996LGBTQ rights in the United States
  3. 2002Timor-Leste
  4. 2009Indonesian Air Force
  5. 2011Mamata Banerjee
  6. 20122012 Northern Italy earthquakes
  7. 2013Enhanced Fujita scale
  8. 20132013 Moore tornado
  9. 2016Singapore
  10. 2019International System of Units
  11. 2022Russo-Ukrainian war

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Everything we record for 2019 →

Sources

Cite this page

“International System of Units”, What's On This Date, https://whatsonthisdate.com/app/event/international-system-of-units-2019-may-20, accessed October 27, 2026.

Cite the underlying source as well — the source links above go to the record this entry is adapted from.

Questions about this entry

When did International System of Units happen?

May 20 2019 — 7 years ago, on a Monday.

Where does this text come from?

Wikipedia “On this day” feed. Summaries are short adaptations that link back to the source, not reprints.

How do I cite this page?

Use the ready-made citation near the sources at the bottom of the page, and follow the source link to cite the underlying record as well.

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